if you want proformance out of the RX75 you should spend more, i have an engine that i got off a john deere SX95 and its currently on my 1962 snapper comet, the engine is a FB460V 12.5 hp engine and the original owner that had the JD SX95 with that engine told me he spent 250 dollors on it and i gotta say it has great proformance and power. what im get at is that the type of muffler will make the proformance